module for cycling through a list of values via a scalar

You use Tie::Cycle to go through a list over and over again. Once you get to
the end of the list, you go back to the beginning. You don't have to worry
about any of this since the magic of tie does that for you.

The tie takes an array reference as its third argument. The tie should
succeed unless the argument is not an array reference. Previous versions
required you to use an array that had more than one element (what's the
pointing of looping otherwise?), but I've removed that restriction since the
number of elements you want to use may change depending on the situation.

During the tie, this module makes a shallow copy of the array reference. If
the array reference contains references, and those references are changed
after the tie, the elements of the cycle will change as well. See the
included test.pl script for an example of this effect.